Transformation, Proliferation, and Influence on Host Performance by Three Gut Bacteria in the Rice Water Weevil (Coleoptera: Curculionidae).

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is one of the most serious pests of rice in the United States and East Asia. Several symbiotic bacteria have been isolated from the gut of this weevil, but none of them have been evaluated for the potential to be paratransgenesis candidates for biological control. We transformed three bacterial strains, Enterococcus faecalis, Bacillus cereus, and Enterobacter sp. isolated from the weevil, with a DsRed-labeled plasmid. We then investigated their fate in the host gut. To assess their biological impacts on the host, we measured adult consumption, survival, egg production, and hatch rate after weevils were inoculated with the transformed bacteria. Our results showed that each of the three bacteria could be successfully transformed. The intestinal bacterial densities were low 2 d after inoculation. However, their populations increased dramatically the following day, regardless whether the adults were fed or starved, and reached their peak abundance 4 d after inoculation. Each strain colonized the adult gut for at least 9-15 d, accumulating mostly in the hindgut. No apparent effects by the transformed strains were observed on weevil performance. In conclusion, due to the ability to colonize the host gut and to ease of culturing, these bacteria might be promising paratransgenesis candidates. They can be engineered and re-introduced into the gut of adult rice water weevils potentially producing effector molecules capable of impairing weevil development and survival. [ABSTRACT FROM AUTHOR]